(1) Field of the Invention
The present invention relates to a polishing system for longitudinal opposite edge faces of a plated steel strip.
(2) Statement of the Prior Art
In the continuous electroplating of the steel strip, a problem arises whereby when a plating electric current is concentrated at opposite edge faces of the steel strip, and consequently a so-called edge-over-coating phenomenon takes place, it results in a plating material being excessively deposited on ends of the steel strip. Since the plated coating which has been deposited excessively on opposite edge faces of the steel strip by the concentrated electric current is in the state of dendrite, and thus it is fragile and easily peeled off, dents will be created on the steel strip by fragments which will be peeled off during press forming operation etc. The edge faces as used herein include longitudinal side faces, upper and lower edge faces along a longitudinal direction on the steel strip.
The present applicant has previously proposed a solution in the Japanese Examined Patent Publication No. Hei 5-41385 entitled as "Polishing System for Opposite Side Faces of the Plated Steel Strip".
The prior art system and its relevant problem will be described hereinbelow, with reference to accompanying drawings for convenience of illustration, wherein;
FIG. 28 is a schematic side view of the prior art polishing system;
FIGS. 29A and 29B are pictorial views showing the edge face of the steel strip which has been warped;
FIGS. 30A-30C are pictorial views illustrating the prior art polishing system while it is being operated to polish the side face of the steel strip;
FIG. 31 is a plan view showing a positional relationship between the conventional cylindrical rotary brush and the steel strip while they are in contact each other;
FIG. 32 is a side view showing a surface where the rotary brush and the side face of the steel strip in FIG. 31 contact each other; and
FIG. 33 is a front elevation showing a prior art cleaning water spray unit.
As shown in FIG. 28, the system as disclosed in the above-described patent publication is designed to remove a plated coating which has been adhered to opposite side surfaces on the steel strip S which has been plated on its dual surfaces, wherein the system comprises at least a pair of side face polishing devices 1 each being arranged along a traveling direction of the steel strip and being adapted to polish opposite side faces of the steel strip S by causing rotary brushes 110 to engage such opposite side faces of the steel strip S in such a manner that the brushes may oppose each other along a widthwise direction of the steel strip S, the rotary axes 111 of the rotary brushes 110 being inclined in the same direction relative to the traveling directions S, said rotary brushes being arranged to be adjacent to each other along the traveling direction of the steel strip S in the same plane of the steel strip, one of said rotary brushes being set to polish the side face on the steel strip from an upward direction to a downward direction, other of said rotary brushes being set to polish the side face from a downward direction to an upward direction, a detector for detecting a variation in a driving load in a motor which operates the rotary brush 110 for rotation, and wherein a signal is sent to a control board, and the control signal is sent to the motor which causes the rotary brushes 110 to travel in the widthwise direction of the steel strip S so as to adjust the position of the rotary brushes 110.
However, even if this system is used, the steel strip is caused to warp at its edge portion under rotary forces of the brush 110, as shown in FIGS. 29A and 29B. If a greater warp is caused to occur, then an adequate brushing effect by means of brush may not be expected.
As above-described, an excessive plating material may deposit on the opposite edge faces on the steel strip, as shown in FIG. 30A. In the case that the steel strip is caused to warp at edge portions under rotary forces of the brush 110, a portion will not be polished at the upper or the lower portion of the edge face of the steel strip as shown in FIG. 30B, after a polishing operation is carried out for the steel strip by means of usual rotary brushes.
An excessive plating portion g unavoidably may not be polished at the upper and the lower portions of the edge faces of the steel strip as shown in FIG. 30C, even when some means are provided to prevent the edge faces of the steel strip S from being warped. In the case, for example, that the conventional cylindrical rotary brush 110 is merely arranged, with an inclination against the edge face on the steel strip as shown in FIG. 31, a contacting face F with the brush may be provided, as shown in FIG. 32. In this case, the side face of the steel strip may be provided with a theoretical contacting face with the brush where no warp may occur. However, the excessive plate deposited portion g may not be eliminated. This reason will be described later.
Rail covers are provided to protect the slidable contact components of the system from the ingress of polishing dusts, and since the rail covers are caused to slide in an interleaving manner (that is, they move slidably in a partially overlapped manner), it may sometimes become impossible to move the rail covers when the polishing dusts have accumulated. Consequently, a portion or the entire length of the edge face on the steel strip will not be polished. For example, in the known system as above-described, removal of the polishing dusts which would fall and accumulate on the rail covers 164, as shown in FIG. 33, has not been concerned. If such polishing dusts are not removed, it may become hard to move the rail covers as above-described, and consequently a carriage cannot be moved.